Heart Attacks in Dogs

Heart attacks in dogs are rare

Vet using a stethoscope to listen to a dog's heart.

GK Hart / Vikki Hart / Getty Images

Heart failure is a common complication of heart disease in dogs. Though canine heart disease includes many different types of conditions, all forms of heart disease can ultimately cause heart failure.

What Is a Heart Attack?

Heart attacks in dogs and cats are rare, but their hearts function similarly to human hearts. The technical term for a heart attack is myocardial infarction, and this occurs when blood flow to the heart wall (the myocardium) is blocked.

Dogs are less likely to suffer heart attacks than humans, but many of the same risk factors are involved: If a dog is obese, has diabetes, has high blood pressure, or contracts a serious bacterial infection, it may be at a greater risk of a heart attack.

If you suspect your dog is having a heart attack, bring it to the vet as soon as possible. There is a version of CPR that can be performed on a dog, but it requires special training to do it correctly. Don't attempt it if you're not trained; you could further injure your dog and waste precious minutes when you could be getting it to the vet's office.

Types of Heart Failure in Dogs

Heart failure in dogs may take on two different forms.

  • Right-sided heart failure occurs when the right side of the heart cannot pump blood properly. This results in the blood, which should be returning to the heart from other parts of the body, backing up in those body organs. Right-sided heart failure usually leads to an accumulation of fluid in the abdominal cavity, the liver, and/or the limbs.​
  • Left-sided heart failure occurs when the pumping mechanism on the left side of the heart fails. In this instance, the blood returning from the lungs to the heart backs up and fluid accumulates in the lungs.

In some dogs, both sides of the heart are involved. This may lead to signs of both right- and left-sided heart failure occurring simultaneously.

Signs of a Heart Attack in Dogs

Dogs with heart disease may be asymptomatic (free of any signs of illness) if the heart disease is mild enough to allow the heart and the rest of the body to compensate. However, if heart disease is severe enough, signs of heart failure will develop over time.

The types of signs seen in heart failure will vary depending on how severe the disease is and which side of the heart is affected. However, the symptoms most commonly encountered with heart failure include:

  • Generalized weakness
  • Tiring easily
  • Depression
  • Lack of appetite
  • Weight loss
  • Coughing
  • Breathing heavily
  • Swelling in the legs (most often seen with right-sided heart failure)
  • A bloated, fluid-filled abdomen (most often seen with right-sided heart failure and also known as ascites)
  • Increased heart rate
  • Weak pulse

Cyanosis (bluish coloration of the gums) may occur if blood circulation is poor and is an indication of inadequate amounts of oxygen reaching the body. Other signs that may occur with heart failure include vomiting, diarrhea, or constipation as a result of poor blood circulation reaching the gastrointestinal tract.

Heart diseases that cause arrhythmias (irregular heartbeats) may cause fainting episodes, which are also known as syncope.

Coughing is often the first sign of canine heart disease and is the most frequent reason dog owners bring their dog to the veterinarian.

Testing Dogs for Heart Disease and Heart Attacks

Since heart attacks in dogs are so rare, your veterinarian will need to rule out many other conditions before diagnosing a heart attack. Other types of heart disease are much more common.

The vet will probably want to rule out heartworms, and in addition to the usual blood and urine tests, will likely order a chest X-ray especially and possibly an ultrasound scan of the heart called an echocardiogram. An electrocardiogram or EKG that measures your dog's heart rhythm can also be helpful. One or more of these tests will be necessary to determine what type of heart disease your dog has.

Treatment and Prevention

The best way to prevent a canine heart attack is to reduce its risk factors: Make sure your dog doesn't get overweight and make frequent visits to the vet to treat any ongoing health conditions, including other types of heart disease.

Right- and left-sided heart failure can often be managed for a period of time using medications that improve heart function and reduce abnormal fluid build-up. Close monitoring is important because medication adjustments will become necessary as the dog's condition changes over time. Keep a close eye on your dog's quality of life and talk to your veterinarian if any concerns arise.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.